Pressure vessels such as a high-pressure tank, in which a substance such as natural gas or hydrogen gas that is in gas form under normal temperatures and pressures is compressed to a high pressure and the compressed substance is filled, are generally known. A vehicle such as a natural gas automobile or a fuel cell automobile is equipped with a pressure vessel in which natural gas or hydrogen gas serving as the fuel is pressurized, filled, and accumulated. It is generally desired that a pressure vessel mounted on a vehicle have a lighter weight for improving fuel efficiency and the like. For this reason, pressure vessels made of fiber reinforced plastics (FRP) such as carbon fiber reinforced plastic (CFRP) and glass fiber reinforced plastic (GFRP) are employed favorably.
JP 2005-069454 A discloses causing a harness to be damaged prior to a gas conduit being damaged so as to cut off electric conduction to a solenoid, thereby closing an electromagnetic valve provided at an end of a hydrogen gas tank, so as to prevent a gas leak that may otherwise occur at the time of a vehicle crash.
Conventionally, when mounting a pressure vessel on a vehicle, the vessel has been mounted at a location such as a rear portion or a central portion of the vehicle, which is relatively less susceptible to shocks and other external influences. However, recently, improvements have been made in pressure resistance of pressure vessels in response to the necessity to increase the fill amount per unit volume, and consequently shock resistance is also improved. Considering this aspect and also considering the desire to reserve riding space or loading space, there are cases in which it is preferred to mount the pressure vessel at a lower portion or a bottom portion of the vehicle, depending on the shape and the application of the vehicle.
When the pressure vessel is mounted at a lower portion or a bottom portion of the vehicle, no inconveniences arise during normal traveling. However, when the vehicle travels on a very bumpy road such as an unpaved road, or when the vehicle passes over an obstacle such as a rock, the road surface or the obstacle may interfere with the lower or bottom portion of the vehicle, and the portion interfered with may become damaged. In such a case, when the pressure vessel becomes damaged to a degree exceeding an acceptable level, it is necessary to immediately detect the damage and/or prevent fluid leakage from the pressure vessel.